Yummy and looks impressive
1. Preheat the oven to 200c
2. Melt the butter in a pan and add the onion and cook for about 5 minutes or until the onion is translucent.
3. Stir in the flour and add the milk a small amount at the time and stir constantly to get a smooth sauce. Once you have got a smooth thick sauce remove it from the heat
4. Add the fish and lemon juice to the sauce and season
5. Cook and wash the spinach by covering it with boiling water and leaving it to cook for a few minutes before draining thoroughly
6. Grease the bottom of a oven proof baking dish and add a 1/3 of the fish sauce, then add a layer of spinach and the lasagna sheets.
7. Repeat until you have used up all the layers and finish with the fish sauce on the top.
8. Sprinkle with parmesan and bake in the oven for 45 minutes.